Vacuum actuated small volume syringe

ABSTRACT

A retractable safety syringe is provided herein wherein an external vacuum compartment produces a retraction force which urges a piston of a plunger toward a retracted position. The retractable safety syringe may have a needle holder which is removably engageable to a distal portion of a syringe body. When the piston is traversed toward the engaged position, the external variable vacuum compartment produces a retraction force. When the piston is traversed to an engaged position, the piston engages the needle holder and disengages the needle holder from the syringe body. The medical professional may release a thumb pressure on a thumb platform of a plunger. At this point, the retraction force of the external variable vacuum compartment may traverse the piston along with the needle holder and needle toward the retracted position and into the syringe body. An internal variable vacuum compartment may also create a retraction force to assist retraction of the needle holder and needle into the syringe body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application of U.S. patentapplication Ser. No. 11/784,797, filed on Apr. 10, 2007, which claimsthe benefits of U.S. Provisional Application No. 60/793,022, filed onApr. 19, 2006, the entire content of which is expressly incorporatedherein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

The present invention relates to a small volume (i.e., about 1 cc orless) retractable safety syringe.

In recent years, the public (e.g., drug addicts, drug users, medicalpersonnel and healthcare providers and the like) has become increasinglyaware of the health hazards associated with needle reuse and accidentalneedle prickings. For example, at least twenty blood-borne pathogens maybe transmitted by the reuse of needles or accidental needle prickings.For example, these blood borne pathogens may include and are not limitedto Human Immunodeficiency Virus (HIV), Acquired ImmunodeficiencySyndrome (AIDS), Hepatitis B, Hepatitis C, syphilis, malaria,tuberculosis, and herpes. Despite the awareness of the risk of needlereuse and accidental needle prickings, at least 36 percent of HIV/AIDScases and more than 50 percent of Hepatitis B and Hepatitis C cases inthe United States may be linked to the sharing of needles among drugaddicts. Accordingly, there is a need to curb the practice of sharingneedles among drug addicts.

The problem of needle sharing or needle reuses is further amplified whenviewed in relation to the world population. For example, approximately30 percent of reported HIV/AIDS cases in Brazil, Chile, Uruguay,Paraguay and Argentina are directly related to the sharing ofcontaminated needles among drug addicts. Approximately 70 percent of theHIV cases reported in China are directly linked to the sharing ofcontaminated needles. In eastern European countries, 80 percent ofinjection drug addicts admit to sharing contaminated needles.Approximately 43 percent of HIV/AIDS cases reported in Poland andYugoslavia are linked to the sharing of contaminated needles among drugaddicts.

Accidental needle prickings also pose a threat to healthcare workers. Inparticular, approximately one million accidental needle prickings arereported by healthcare workers annually. However, it is believed that atleast three million accidental needle prickings occur each year, ofwhich about two million are unreported. Various studies estimate thatout of all the accidental needle pricking injuries that occur to nurses,approximately 40 percent to 53 percent go unreported. Various studiesalso estimate that out of all the needle pricking injuries that occur tolaboratory technicians, approximately 92 percent go unreported. Variousstudies further estimate that out of all the needle pricking injuriesthat occur to physicians, approximately 70 percent to 95 percent gounreported.

In 1997, the Center for Disease Control and Prevention (CDC) sponsored astudy which found that approximately 76 percent of needle prickinginjuries could be avoided by using safety needles. Presently, there areat least 250 types of safety syringes. Unfortunately, the safetysyringes that currently exist have been criticized for various problemsassociated in operating the safety syringe and its ineffectiveness.

One type of safety syringe is a vacuum assisted safety syringe whereinthe needle of the syringe is retracted into a syringe body after apiston engages a needle holder due to a retraction force of a variablevacuum compartment. The retraction force of the variable vacuumcompartment is a function of the size and volume of the variable vacuumcompartment as the plunger is traversed from a retracted position to anengaged position. If the variable vacuum compartment is not sufficientlylarge, then the retraction force of the variable vacuum compartment maynot be sufficient to withdraw the needle holder and needle into thesyringe body. This problem is particularly pronounced when theretractable safety syringe has a small variable fluid chamber of about 1cc or less. Small variable fluid chambers require a syringe body havinga small diameter. Correspondingly, the variable vacuum compartment isalso small limiting its maximum potential retraction force. If theretraction force of the variable vacuum compartment is not greater thana force required to traverse the needle holder and needle into thesafety syringe, then the needle will still be exposed outside of thesyringe body thereby possibly pricking a medical professional orallowing a drug addict to reuse the needle.

Accordingly, there is a need in the art for an improved safety syringe.

BRIEF SUMMARY

The retractable safety syringe discussed herein resolves the issuesdiscussed above, discussed below and those that are known in the art.

The retractable safety syringe may have a syringe body, plunger, needleholder and needle. The plunger which may comprise a piston and a rigidshaft may be disposed within the syringe body. The needle may beattached to the needle holder. Also, the needle holder may be removeablyengageable to the syringe body. The volume defined by the needle holder,syringe body and the piston may be referred to as a variable fluidchamber. On the opposed side of the piston within the syringe body is aninternal variable vacuum compartment. The internal variable vacuumcompartment may be defined by the piston, syringe body and a proximalseal through which the rigid shaft extends. The piston forms an airtightand fluid tight seal with the syringe body. Also, the proximal seal mayform an airtight seal between the syringe body and the rigid shaft. Whenthe piston is traversed toward an engaged position, no air molecules areintroduced into the internal variable vacuum compartment therebyproducing a retraction force urging the piston back toward a retractedposition.

The syringe may also have an external variable vacuum compartment whichalso produces a retraction force urging the piston back toward theretracted position when the piston is traversed toward the engagedposition. The external variable vacuum compartment may be defined by arigid shell, the syringe body, proximal seal and a shell seal. The rigidshell may be disposed over the syringe body. A distal portion of therigid shell may have the shell seal which provides an airtight sealbetween the rigid shell and the syringe body. The proximal seal mayprovide an airtight seal between the proximal portion of the syringebody and the rigid shell. When the piston is traversed toward theengaged position, the external variable vacuum compartment is increasedin volume without any addition of air molecules thereby producing aretraction force. The retraction force of the external variable vacuumcompartment urges the piston back toward the retracted position.

It is contemplated that the piston may be urged back toward theretracted position by the retraction force created by the externalvariable vacuum compartment. Also, the piston may be urged back towardthe retracted position by the retraction forces created by the externalvariable vacuum compartment and another mechanism (e.g., spring, etc.).As a further alternative, it is contemplated that the piston may beurged back toward the retracted position by the retraction forcescreated by both the external and internal variable vacuum compartments.

The piston may be engageable to the needle holder when the piston istraversed to the engaged position. By way of example and not limitation,the piston may be formed with longitudinal offset tabs that engage aflange of the needle holder.

In use, the safety syringe may be provided to the medical professionalwith fluidic medication filled in the variable fluid chamber. To injecta patient, the medical professional may invert the syringe such that theneedle is pointing upward. The medical professional may tap the syringeto dislodge any air bubbles within the variable fluid chamber toward theneedle. The piston is slightly traversed toward the engaged position toremove the trapped air bubbles within the variable fluid chamber. Theexternal and internal variable vacuum compartments produces retractionforces which urge the piston back toward the retracted position.Accordingly, the medical professional maintains thumb pressure on athumb platform to prevent reintroducing air into the variable fluidchamber.

The medical professional injects the fluid medication into the patientby traversing the piston to the engaged position. At the engagedposition, the piston engages the needle holder and the needle holder isdisengaged from the syringe body. The medical professional may removehis/her thumb pressure from the thumb platform such that the retractionforces of the external and internal variable vacuum compartments urgethe piston, needle holder and needle into the syringe body. Once theneedle is withdrawn into the syringe body, the needle may be cantedtoward one side of the syringe body. The syringe cannot be reused thuspreventing accidental needle pricking and reuse of the syringe.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is a perspective view of a retractable safety syringe;

FIG. 2 is a cross sectional perspective view of the syringe shown inFIG. 1;

FIG. 3 is an enlarged cross sectional perspective view of a distalportion of the syringe shown in FIG. 2;

FIG. 4 is an enlarged cross sectional view of the distal portion of thesyringe with a piston disposed at a filling position; and

FIG. 5 is an enlarged cross sectional view of the distal portion of thesyringe with the piston disposed at an engaged position; and

FIG. 6 is a front cross sectional view of the syringe with a needle ofthe syringe retracted into a syringe body and canted toward one side ofthe body.

DETAILED DESCRIPTION

Referring now to the drawings which are for the purposes of illustratingthe preferred embodiments of a retractable safety syringe 10 and not forthe purpose of limiting the same, FIG. 1 is a perspective view of theretractable safety syringe 10 with an external variable vacuumcompartment 12 (see FIG. 2) for creating a retraction force to retract aneedle 14 of the retractable safety syringe 10 within the retractablesafety syringe 10 so as to prevent accidental needle pricking and needlereuse. Although the discussion provided herein regarding the retractablesafety syringe 10 is made in relation to small volume syringes (i.e.,about 1 cc or less), it is also contemplated that the various aspects ofthe retractable safety syringe 10 may also be variously embodied andemployed in large volume safety syringes (i.e., 1 cc or more).

The retractable safety syringe 10 may comprise a syringe body 16defining a distal portion and a proximal portion. A needle holder 18 maybe removably engaged to the distal portion of the syringe body 16. Also,a needle 14 may be fixedly engaged to the needle holder 18 and protrudecoaxially out of the syringe body 16. The retractable safety syringe 10may also comprise a plunger 20 having a piston 22 traversable within thesyringe body 16 between a retracted position and an engaged position.The plunger 20 may also comprise a rigid shaft 24 disposed within thesyringe body 16 and engaged to the piston 22. The rigid shaft 24 mayextend out of the syringe body 16 through the proximal portion of thesyringe body 16 and may be coaxially aligned with the syringe body 16. Athumb platform 26 may be attached to the proximal portion of the rigidshaft 24. Also, the thumb platform 26 may be operative to traverse thepiston 22 between the retracted position and the engaged position. Theplunger 20 may also comprise a rigid shell 28 engaged to the proximalportion of the rigid shaft 24. The rigid shell 28 may extend over thesyringe body 16 and terminate at about the distal portion of the rigidshaft 24 or the piston 22. A proximal seal 30 may be interposed betweenthe proximal portion of the syringe body 16 and the inner surface 32 ofthe rigid shell 28. The proximal seal 30 forms an air tight seal betweenthe syringe body 16 and the rigid shell 28. A shell seal 34 may bedisposed on the distal portion of the rigid shell 28 and be engaged tothe outer surface 36 of the syringe body 16.

The volume defined by the proximal seal 30, shell seal 34, rigid shell28 and syringe body 16 defines a first variable vacuum compartment or anexternal variable vacuum compartment 12. In use, the external variablevacuum compartment 12 produces a retraction force that urges the plunger20 toward the retracted position when the piston 22 is traversed towardthe engaged position. For example, when the medical professional injectsthe patient with the fluidic medication, the piston 22 is traversed tothe engaged position. At this point, the piston 22 engages the needleholder 18. When the medical professional releases the thumb platform 26,the retraction force of the external variable vacuum compartment 12urges the piston 22 as well as the needle holder 18 and needle 14 towardthe retracted position. The needle 14 is withdrawn into the syringe body16 and is no longer exposed such that there is no risk of accidentalneedle pricking and the needle 14 may not be reused.

The retractable safety syringe 10 may comprise the needle 14, needleholder 18, syringe body 16, plunger 20, and a carriage 38. The syringebody 16, plunger 20 and carriage 38 may be generally coaxially alignedwith each other such that the plunger 20 (i.e., rigid shell 28 andpiston 22) may be slidably traversable between the carriage 38 and thesyringe body 16 and within the syringe body 16. The carriage 38 may havea U-shaped configuration (see FIG. 1), as discussed in detail below, agenerally cylindrical configuration (not shown) or other configuration.The carriage 38 may define an inner cavity 40. The syringe body 16 mayreside or be disposed within the inner cavity 40 of the carriage 38. Thecarriage 38 may define a distal portion and a proximal portion. Thedistal portion may have a rounded configuration and extend radiallyinward. The distal portion of the carriage 38 may be fixedly engaged tothe distal portion of the syringe body 16. By way of example and notlimitation, the distal portion of the carriage 38 may be fixedly engagedto the distal portion of the syringe body 16 via sonic welding,adhesive, or other temporary or permanent joining methods.

The syringe body 16 may have a generally cylindrical configuration. Aninner volume of the syringe body 16 may contain the piston 22, rigidshaft 24 and the needle holder 18. Preferably, the rigid shaft 24 isfixedly engaged to the piston 22. The piston 22 is traversable betweenthe engaged position and the retracted position. At the engagedposition, the piston 22 is disposed adjacent the distal portion of thesyringe body 16 and engaged to the needle holder 18, as shown in FIG. 5.At the retracted position, the piston 22 is generally disposed adjacentthe proximal portion of the syringe body 16. The rigid shaft 24 extendsthrough the proximal portion of the syringe body 16. A proximal portionof the rigid shaft 24 is disposed external to the syringe body 16. Athumb platform 26 may be engaged to the proximal portion of the rigidshaft 24. The piston 22 may be traversable between the engaged positionand the retracted position by pushing or pulling the thumb platform 26in relation to the syringe body 16. The thumb platform 26 may have agenerally circular disc configuration. The thumb platform 26 may besufficiently large to provide thumb support to the thumb of the medicalprofessional as the medical professional depresses the thumb platform 26to traverse the piston 22 toward the engaged position. Also, the thumbplatform 26 may have an underside surface 42 which may be sufficientlylarge such that the medical professional may grasp the thumb platform 26with his/her fingers to pull the thumb platform 26 to traverse thepiston 22 toward the retracted position.

The plunger 20 may also comprise a rigid shell 28 having a cylindricalconfiguration. Other configurations are also contemplated such assquare, pentagonal, oval, etc. The rigid shell 28 may be interposedbetween the carriage 38 and the syringe body 16. The rigid shell 28 maydefine an open distal portion and a partially open proximal portion. Thedistal portion of the rigid shell 28 may have an inwardly directedflange 44. A shell seal 34 may be disposed about an inner periphery ofthe inwardly directed flange 44 of the rigid shell distal portion. Theshell seal 34 may also be slidingly engageable with an outer surface 36of the syringe body 16. The shell seal 34 may provide an airtight sealbetween the rigid shell 28 and the syringe body 16. More particularly,the shell seal 34 may provide an airtight seal between the distalportion of the rigid shell 28 and the outer surface 36 of the syringebody 16. In use, as the piston 22 is traversed between the engagedposition and the retracted position, the shell seal 34 slides on theouter surface 36 of the syringe body 16 between the proximal portion andthe distal portion of the syringe body 16.

The proximal portion of the syringe body 16 may have an outwardlydirected flange 46. A proximal seal 30 may be disposed about an outerperiphery of the outwardly directed flange 46 of the syringe body 16proximal portion. The proximal seal 30 may also slidingly engage theinner surface 32 of the rigid shell 28. The proximal seal 30 may form anairtight seal between the syringe body 16 and the rigid shell 28. Moreparticularly, the proximal seal 30 may provide an airtight seal betweenthe proximal portion of the syringe body 16 and the inner surface 32 ofthe rigid shell 28. The proximal seal 30 may provide the airtight sealagainst the inner surface 32 of the rigid shell 28 as the piston 22 istraversed between the engaged position and the retracted position.

The first variable vacuum compartment or the external variable vacuumcompartment 12 defined by the proximal seal 30, shell seal 34, syringebody 16 and rigid shell 28 increases in volume as the plunger 20 istraversed toward the engaged position. Conversely, the external variablevacuum compartment 12 decreases in volume as the plunger 20 is traversedtoward the retracted position. Initially, the safety syringe 10 may beprovided to the medical professional with the plunger 20 in theretracted position. When the medical professional depresses the thumbplatform 26 to traverse the piston 22 toward the engaged position, theexternal variable vacuum compartment 12 increases in volume without anyadditional air molecules being introduced into the external variablevacuum compartment 12. A vacuum is created in the external variablevacuum compartment 12 when the plunger 20 is traversed toward theengaged position producing a retraction force which urges the plunger 20toward the retracted position.

The proximal portion of the syringe body 16, rigid shaft 24, and rigidshell 28 defines a proximal compartment 48. The proximal compartment 48does not have a vacuum when the plunger 20 is traversed toward theretracted position because as the plunger 20 is traversed toward theretracted position, air molecules from the environment is introducedinto the proximal compartment 48 through an air vent 50. Also, theproximal compartment 48 does not compress air when the piston 22 istraversed toward the engaged position because as the plunger 20 istraversed to the engaged position, air molecules within the proximalcompartment 48 may escape out of the proximal compartment through theair vent 50. As such, as the plunger 20 is traversed between the engagedposition and the retracted position, the proximal compartment does notproduce a retraction force which urges the plunger 20 toward theretracted position or an extension force which urges the plunger 20toward the extended position.

As discussed above, the proximal seal 30 engages the proximal portion ofthe syringe body 16 and slidingly engages the inner surface 32 of therigid shell 28. Additionally, the proximal seal 30 may extend from theproximal portion of the syringe body 16 and slidingly engage the outersurface 54 of the rigid shaft 24 of the plunger 20. The proximal seal 30may provide an airtight seal between the rigid shaft 24 of the plunger20 and the syringe body 16. More particularly, the proximal seal 30 mayprovide an airtight seal between the proximal portion of the syringebody 16 and an outer surface 54 of the rigid shaft 24 of the plunger 20.Also, a piston seal 56 may be disposed about an outer periphery of thepiston 22 which provides an airtight and fluid tight seal between thepiston 22 and the syringe body 16. More particularly, the piston seal 56may be disposed within an undercut groove 58 of the piston 22 formedabout an outer diameter of the piston 22. The piston seal 56 may beslidingly engaged to the inner surface 60 of the syringe body 16. As thepiston 22 is traversed toward the retracted position and toward theengaged position, the piston seal 56 slides along the inner surface 60of the syringe body 16 and may have an airtight seal and a fluid tightseal against the inner surface 60 of the syringe body 16. Also, theproximal seal 30 may slide against the outer surface 54 of the rigidshaft 24 of the plunger 20 as the plunger 20 is traversed between theretracted position and the engaged position.

The proximal seal 30, the piston seal 56, syringe body 16 and rigidshaft 24 may define a second variable vacuum compartment or an internalvariable vacuum compartment 62. Initially, when the retractable safetysyringe 10 is provided to the medical professional, the plunger 20 maybe in the retracted position. As the plunger 20 is traversed toward theengaged position, the internal variable vacuum compartment 62 mayincrease in volume. Also, since the piston seal 56 and proximal seal 30create an airtight seal between the syringe body 16 and the rigid shaft24, a vacuum is formed in the internal variable vacuum compartment 62.The vacuum produces a retraction force which urges the plunger 20 andpiston 22 toward the retracted position as the plunger 20 is traversedtoward the engaged position.

In use, when the plunger 20 is traversed to the engaged position, thepiston 22 of the plunger 20 engages the needle holder 18. The retractionforce of the external variable vacuum compartment 12 and the internalvariable vacuum compartment 62 traverses the piston 22 as well as theneedle holder 18 and needle 14 into the syringe body 16. The retractionforce of the external variable vacuum compartment 12 may be increased byincreasing the inner diameter 64 of the rigid shell 28 over the outerdiameter 66 of the syringe body 16. As the inner diameter 64 of therigid shell 28 increases over the outer diameter 66 of the syringe body16, the volume of the external variable vacuum compartment 12 measuredwhen the plunger 20 is at the engaged position increases. The increasedvolume creates a larger retraction force. With respect to the internalvariable vacuum compartment 62, the retraction force of the internalvariable vacuum compartment 62 may be increased by reducing the outerdiameter of the rigid shaft 24 or increasing the inner diameter of thesyringe body 16. As such, when the plunger 20 is traversed to theengaged position, the internal variable vacuum compartment 62 is alsoincreased thereby producing a greater retraction force.

It is contemplated that the proximal seal 30 may engage the proximalportion of the syringe body 16 and only the shell (i.e., inner surface32 of the shell 28) to form the external variable vacuum compartment 12.No internal variable vacuum compartment is formed. In this instance, theexternal variable vacuum compartment 12 is sized to provide a sufficientretraction force to withdraw the needle 14 into the syringe body 16after the piston 22 has engaged the needle holder 18. Alternatively, itis contemplated that the proximal seal 30 may engage the proximalportion of the syringe body 16 and both the rigid shell 28 and the shaftof the plunger 20 (see portion 52 in FIG. 2), and more particular, theinner surface 32 of the shell 28 and the outer surface 54 of the shaft24. In this instance, the external and internal variable vacuumcompartments 12, 62 are sized to provide sufficient retraction forces towithdraw the needle 14 into the syringe body 16 after the piston 22 hasengaged the needle holder 18.

The carriage 38 may have a U-shaped configuration, as shown in FIGS. 1and 2. The carriage 38 may define a proximal portion and a distalportion. The carriage 38 may have finger platforms 68 formed on theproximal portion of the carriage 38. The finger platforms 68 areoperative to provide leverage such that the medical professional maypush or pull the plunger 20 with respect to the syringe body 16. Thedistal portion of the carriage 38 may have a flat bottom configurationwith an aperture formed therethrough. The flat bottom may also have acap 70 (see FIG. 1) for receiving a distal portion of the syringe body16. The cap 70 may be fixedly engaged to the distal portion of thesyringe body 16 via sonic welding, adhering, friction fit, and othermethods known in the art. Throughout the operation of the retractablesafety syringe 10, the distal portion of the syringe body 16 may befixedly engaged to the distal portion of the carriage 38. Also, aproximal portion of the carriage 38 may have an optional bridge whichconnects proximal portions of tines of the carriage 38. The bridgesprevent the proximal portions of the carriage tines from compressingonto the outer surface of the rigid shell 28 thereby creating frictionbetween the carriage 38 and the rigid shell 28. Such friction mayprevent the retraction forces of the internal variable vacuumcompartment 62 and/or the external variable vacuum compartment 12 fromretracting the needle holder 18 and needle 14 into the syringe body 16.

The needle holder 18 may be removeably engageable to the distal portionof the syringe body 16. In particular, the needle holder 18 may have aretaining surface 72 and a releasing surface 74, as shown in FIGS. 3-5.The retaining surface 72 may be disposed immediately above the releasingsurface 74. The retaining surface 72 may have an outer diameter which islarger than the releasing surface 74. Initially, when the needle holder18 is engaged to the syringe body 16, a retaining member 76 may beinterposed between the retaining surface 72 and the inner surface 60 ofthe syringe body 16. The retaining member 76 may frictionally engage theinner surface 60 of the syringe body 16 and may also frictionally engagethe retaining surface 72 of the needle holder 18.

The retaining member 76 may be disposed about the retaining surface 72or the releasing surface 74. When the retaining member 76 is disposedabout the retaining surface 72, the retaining member 76 is in a firstposition. When the retaining member 76 is disposed about the releasingsurface 74, the retaining member 76 is in a second position. When theretaining member 76 is disposed about the releasing surface 74 (see FIG.5), the retaining member 76 may frictionally engage the inner surface 60of the syringe body 16 but may be disengaged from the releasing surface74. As such, the needle holder 18 may be retracted into the syringe body16 under the retraction forces of the external and/or internal variablevacuum compartments 12, 62. When the retaining member 76 is disposedabout the retaining surface 72 (see FIG. 4), the retaining member 76 mayprovide a fluidic seal between the needle holder 18 and the syringe body16.

The distal portion of the syringe body 16 may have an inwardly directedflange 80 and a through hole may be formed through the distal portion ofthe syringe body 16. The needle holder 18 may be partially disposedwithin the syringe body 16 and also extend through the aperture of thedistal portion of the syringe body 16. An inner diameter of the apertureof the distal portion of the syringe body 16 may be about equal to anouter diameter of a holding surface 82 of the needle holder 18. Thejunction between the holding surface 82 and the releasing surface 74 maydefine a lip 84 which abuts the inwardly directed flange 80 of thesyringe body 16. As discussed above, the retaining member 76 may betraversed from the first position to the second position. When theretaining member 76 is traversed to the second position from the firstposition, the needle holder 18 is urged downwardly due to frictionalforces. The lip 84 and the inwardly directed flange 80 of the distalportion of the syringe body 16 contact each other and provide aresisting force to prevent downward movement of the needle holder 18.

To traverse the retaining member 76 from the first position to thesecond position, the piston 22 may be formed with a punch 86. The punch86 may be formed on the distal portion of the piston 22. The punch 86may have a cylindrical configuration and be sized and configured to matewith the retaining member 76. More particularly, the punch 86 may have alower surface 88 which mates with an upper surface 90 of the retainingmember 76. When the piston 22 is traversed toward the engaged position,the lower surface 88 of the punch 86 contacts the upper surface 90 ofthe retaining member 76. When the piston 22 is further traversed to theengaged position, the punch 86 creates a force greater than thefrictionally forces between the retaining member 76 with the syringebody 16 and retaining surface 72 of the needle holder 18. The punch 86of the piston 22 displaces the retaining member 76 from the firstposition to the second position. Also, the lip 84 contacts the inwardlydirected flange 80 of the syringe body 16 distal portion and preventsthe needle holder 18 from being pushed out of the syringe body 16.

At about the moment that the retaining member 76 is traversed from thefirst position to the second position, the piston 22 engages the needleholder 18 (see FIG. 5). In particular, the proximal portion of theneedle holder 18 may have an outwardly directed flange 92. Also, thepiston 22 may have longitudinal offset tabs 94 which engage the needleholder 18, and more particularly, the outwardly directed flange 92 ofthe needle holder 18. The engagement between the outwardly directedflange 92 and the longitudinal offset tabs 94 is discussed in moredetail in U.S. Pat. No. 6,413,236, issued to Van Dyke, the entirecontent of which is expressly incorporated herein by reference. Thelongitudinal offset tabs 94 engage the outwardly directed flange 92 ofthe needle holder 18 such that when the piston 22 is withdrawn into thesyringe body 16 via the retraction force, the needle 14 is also cantedtoward one side of the syringe body 16, as shown in FIG. 6. Inparticular, the longitudinal offset tabs 94 may comprise an upperproximal block tab 104 and a lower distal wedge tab 106 (see FIG. 4).The lower distal wedge tab 106 passes and hooks onto the flange of theneedle holder 18 when the piston 22 is traversed to the engaged position(see FIG. 5). The upper proximal block tab 104 does not pass theoutwardly directed flange 92 of the needle holder 18 when the piston 22is traversed to the engaged position (see FIG. 5). Rather, the upperproximal block tab 104 pushes down on the outwardly directed flange 92of the needle holder 18. When the needle 14 and needle holder 18 areretracted into the syringe body 16, the upper proximal block tab 104pushes down on the outwardly directed flange 92 of the needle holder 18and the lower distal wedge tab 106 pulls up on the outwardly directedflange 92 of the needle holder 18 to cant the needle 14 to one side ofthe syringe (see FIG. 6).

The needle holder 18 may also have a proximally facing frust conicalsurface 96 (see FIG. 4). Also, the piston 22 may have a frusto conicalcone 98 protruding out of a distal portion of the piston 22. The frustoconical cone 98 may mate with the frust conical surface 96 when thepiston 22 is traversed to the engaged position to eject as much fluidicmedication out of a variable fluid chamber 100. The variable fluidchamber 100 is the volume defined by the needle holder 18, piston 22 andsyringe body 16.

Although the retractable safety syringe 10 discussed herein is inrelation to small volume safety syringe having a variable fluid chamber100 sized at about 1 cc or less, the external variable vacuumcompartment 12 may be employed and embodied on the retractable safetysyringes on large retractable safety syringes having a variable fluidchamber 100 sized greater than 1 cc or more.

In use, the retractable safety syringe 10 may be provided to medicalprofessionals with fluidic medication pre-filled in the variable fluidchamber 100. If the variable fluid chamber 100 is filled/pre-filled withfluidic medication, then the retractable safety syringe 10 is providedto the medical professional with the plunger 20 in the retractedposition. In this state, the external variable vacuum compartment 12and/or internal variable vacuum compartment 62 does not produce aretraction force which urges the plunger 20 toward the retractedposition. To inject the fluidic medication into the patient, the medicalprofessional may invert the retractable safety syringe 10 such that theneedle 14 is pointed upward. The medical professional may tap thecarriage 38 or the retractable safety syringe 10 to dislodge any airbubbles within the variable fluid chamber 100 toward the needle 14. Themedical professional may slightly depress the thumb platform 26 to ejectthe air bubbles out of the variable fluid chamber 100. The medicalprofessional may maintain thumb pressure on the thumb platform 26 suchthat the piston 22 does not traverse back toward the retracted positionand reintroduce air into the variable fluid chamber 100.

The medical professional then inserts the needle 14 into the body of thepatient. After insertion, the medical professional depresses the thumbplatform 26 to traverse the piston 22 toward the engaged position. Asthe piston 22 is traversed toward the engaged position, the internaland/or external variable vacuum compartments 62, 12 increase in volumewithout any additional air molecules being introduced into the externaland/or internal variable vacuum compartments 12, 62. A vacuum is createdin the external and/or internal variable vacuum compartments 12, 62which produce retraction forces which urge the plunger 20 and piston 22back toward the retracted position. As long as the thumb of the medicalprofessional applies pressure to the platform, the piston 22 is nottraversed back toward the retracted position.

The plunger 20 is further traversed to the engaged position. At theengaged position, the retraction forces of the internal and externalvariable vacuum compartments 62, 12 are sufficient to withdraw theneedle holder 18 and needle 14 into the syringe body 16. Also, the lowersurface 88 of the punch 86 of the piston 22 contacts the upper surface90 of the retaining member 76. The punch 86 pushes the retaining member76 off of the retaining surface 72 and about the releasing surface 74thereby traversing the retaining member 76 from the first position tothe second position. The lip 84 of the needle holder 18 and the inwardlydirected flange 80 of the syringe body 16 prevent the needle holder 18from being pushed out of the syringe body 16 through its distal portion.At about the time the retaining member 76 is traversed to the secondposition, the piston 22 engages the needle holder 18 via thelongitudinal offset tabs 94 and the outwardly directed flange 92 of theneedle holder 18. Any frictional force between the needle holder 18 andsyringe body 16 and also between the piston 22, piston seal 56 andsyringe body 16 may be less than the retraction forces of the externaland/or internal variable vacuum compartments 12, 62. At the engagedposition, the frusto conical cone 98 mates with the frusto conicalsurface 96 of the needle holder 18. Most of the fluidic medication isinjected into the patient. The medical professional releases the thumbplatform 26 and the retraction forces of the external and/or internalvariable vacuum compartments 12, 62 urges the piston 22 as well as theneedle holder 18 and needle 14 into the syringe body 16.

If the fluidic medication is not pre-filled into the variable fluidchamber 100, the medical professional may fill the variable fluidchamber 100 with fluidic medication. Initially, the retractable safetysyringe 10 may be provided to the medical professional with the piston22 in the retracted position. The medical professional may depress thethumb platform 26 to traverse the piston 22 to a filling position. Thefilling position is when the piston 22 is between the retracted positionand the engaged position. Preferably, the filling position is when thepiston 22 is closely adjacent to the needle holder 18 (see FIG. 4). Byway of example and not limitation, the piston 22 may be characterized asbeing closely adjacent to the needle holder 18 when the piston 22 iscloser to the needle holder 18 than the proximal portion of the syringebody 16 or the punch 86 of the piston 22 contacts the retaining member76 and has not displaced the retaining member 76 off of the retainingsurface 72. Once the piston 22 is in the filling position (i.e., pistonadjacent the needle holder 18), the medical professional may insert theneedle 14 into a medication container containing fluidic medication. Themedical professional slowly releases pressure on the thumb platform 26to permit the retraction forces of the external and/or internal variablevacuum compartments 12, 62 to traverse the piston 22 back toward theretracted position. As the piston 22 is traversed back toward theretracted position, fluidic medication inside of the medical containeris transferred into the variable fluid chamber 100.

The medical professional may continue to release pressure on the thumbplatform 26 until an appropriate amount of fluidic medication iscontained in the variable fluid chamber 100. Optionally, the syringebody 16 may be fabricated from a clear material having volumetricgraduations 102 (see FIG. 1) imprinted on an outer surface 36 of thesyringe body 16. The medical professional may determine the amount offluidic medication contained within the variable fluid chamber 100 byviewing the position of the piston 22 with respect to the volumetricgraduation 102. When the appropriate amount of fluidic medication iscontained within the variable fluid chamber 100, the medicalprofessional removes the needle 14 from the medication container. Themedical professional maintains thumb pressure on the thumb platform 26such that air is not introduced into the variable fluid chamber 100. Themedical professional inverts the needle 14 and taps the retractablesafety syringe 10 to dislodge air bubbles within the variable fluidchamber 100 toward the needle 14 and depresses the thumb platform 26 toeject any air bubbles within the variable fluid chamber 100. Theretractable safety syringe 10 is now prepared to inject the fluidicmedication into the patient and may be injected into the patient via thesteps discussed above.

The syringe 10 discussed herein provides for a sterile environmentwithin the variable fluid chamber 100 such that fluidic medicationfilled within the variable fluid chamber 100 is not contaminated by thehandling (e.g., touching outer surface 54 of plunger shaft 24) of thesyringe 10 by the user or medical professional. The reason is that theproximal seal 30 is an airtight seal that prevents contaminates fromentering the syringe body 16 (i.e., variable vacuum compartment 62)through its proximal portion. Moreover, the piston seal 56 provides anadditional barrier to prevent contaminates from entering the variablefluid chamber 20 through the proximal portion of the syringe body 16.Furthermore, the rigid shell 28 provide for an additional barrier tocontamination. The rigid shell 28 is disposed over shaft 24 such that aphysical barrier exits between the outer surface 54 of the shaft 24 andthe medical professional's fingers such that during use of the syringe10, no contact is made with the medical professional and the outersurface 42 of the shaft 30.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein. Further, the various features of the embodimentsdisclosed herein can be used alone, or in varying combinations with eachother and are not intended to be limited to the specific combinationdescribed herein. Thus, the scope of the claims is not to be limited bythe illustrated embodiments.

1. A vacuum retractable safety syringe, comprising: a syringe bodyhaving a distal end and a proximal end; a piston disposed within thesyringe body and extending through the proximal end of the syringe body,the plunger being traversable between a retracted position and anengaged position; a needle assembly removeably engageable to the distalportion of the syringe body; a variable fluid chamber in fluidcommunication with the external environment through the needle assembly,the piston forming a proximal wall of the variable fluid chamber, theplunger configured to reduce the volume of the variable fluid chamberwhen the plunger is traversed toward the engaged position; a variablevacuum chamber sealed from the external environment, the variable vacuumchamber increasing in volume as the piston is traversed toward theengaged position and creating a force in a proximal direction whichretracts the needle assembly into the syringe body when the needleassembly is released from engagement with the distal portion of thesyringe body; wherein a diameter of the variable fluid chamber is lessthan a diameter of the variable vacuum chamber.
 2. The syringe of claim1, further comprising: a shell attached to the piston and disposedexternal to the syringe body, the shell and the syringe body defining anexternal vacuum compartment wherein the external vacuum compartmentcreates a retraction force as the piston is traversed toward the engagedposition.
 3. The syringe of claim 2, wherein the external vacuumcompartment is defined by the shell, the syringe body, a proximal sealattached to the proximal portion of the syringe body configured to forman air tight seal between an inner surface of the shell and the proximalportion of the syringe body, and a shell seal attached to a distalportion of the shell configured to form an air tight seal between thedistal portion of the shell and an outer surface of the syringe body. 4.The syringe of claim 2, wherein the external vacuum compartmentcircumscribes the syringe body.
 5. The syringe of claim 1, wherein thesyringe body defines an internal vacuum compartment isolated from theexternal vacuum compartment, and the internal vacuum compartment createsa second retraction force as the piston is traversed toward the engagedposition such that after the plunger engages the needle at the engagedposition the first and second retraction forces of the internal andexternal vacuum compartments traverses the needle assembly into thesyringe body.
 6. The syringe of claim 5, wherein the internal vacuumcompartment is defined by the syringe body, the piston, a piston sealdisposed about the piston and a proximal seal attached to the proximalportion of the syringe body configured to provide an air tight sealbetween the syringe body and a shaft slidingly traversable through theproximal seal.
 7. The syringe of claim 1, wherein the variable fluidchamber has a volume of about 1 cc or less when the piston is fullyretracted.
 8. The syringe of claim 1, wherein the piston is configuredto engage the needle assembly when the piston is fully traversed towardthe distal end of the syringe body, the engagement causing the needleassembly to be released from engagement with the distal end of thesyringe body.
 9. The syringe of claim 1, wherein the variable fluidchamber is pre filled with fluidic medication when the syringe issupplied to a medical professional.
 10. The syringe of claim 1, furthercomprising a carriage fixedly attached to the distal portion of thesyringe body, the shell being slideably disposed within the carriage.11. A vacuum retractable safety syringe, comprising: a syringe bodyhaving a distal end and a proximal end; a piston disposed within thesyringe body and extending through the proximal end of the syringe body,the piston being traversable between a retracted position and an engagedposition; a needle assembly removeably engageable to the distal portionof the syringe body; a variable fluid chamber in fluid communicationwith the external environment through the needle assembly, the pistonforming a proximal wall of the variable fluid chamber, the pistonconfigured to reduce the volume of the variable fluid chamber when thepiston is traversed toward the engaged position; a variable vacuumchamber sealed from the external environment, the variable vacuumchamber increasing in volume as the piston is traversed toward theengaged position and creating a force in a proximal direction whichretracts the needle assembly into the syringe body when the needleassembly is released from engagement with the distal portion of thesyringe body; wherein the at least a portion of the variable vacuumchamber circumscribes at least a portion of the variable fluid chamber.12. The syringe of claim 11, wherein the variable fluid chamber has avolume of about 1 cc or less when the piston is fully retracted.
 13. Thesyringe of claim 11, wherein the piston is configured to engage theneedle assembly when the piston is fully traversed toward the distal endof the syringe body, the engagement causing the needle assembly to bereleased from engagement with the distal end of the syringe body. 14.The syringe of claim 11, wherein the volume of the variable fluidchamber when the piston is fully retracted is about 1 cc or less.